{
  "id": "2008.11723",
  "version": "v1",
  "published": "2020-08-26T18:00:00.000Z",
  "updated": "2020-08-26T18:00:00.000Z",
  "title": "Short Term Variability of Evolved Massive Stars with TESS II: A New Class of Cool, Pulsating Supergiants",
  "authors": [
    "Trevor Z. Dorn-Wallenstein",
    "Emily M. Levesque",
    "Kathryn F. Neugent",
    "James R. A. Davenport",
    "Brett M. Morris",
    "Keyan Gootkin"
  ],
  "comment": "29 pages, 13 figures, 8 tables. Accepted for publication in ApJ. Comments welcome",
  "categories": [
    "astro-ph.SR"
  ],
  "abstract": "Massive stars briefly pass through the yellow supergiant (YSG) phase as they evolve redward across the HR diagram and expand into red supergiants (RSGs). Higher-mass stars pass through the YSG phase again as they evolve blueward after experiencing significant RSG mass loss. These post-RSG objects offer us a tantalizing glimpse into which stars end their lives as RSGs, and why. One telltale sign of a post-RSG object may be an instability to pulsations, depending on the star's interior structure. Here we report the discovery of five YSGs with pulsation periods faster than 1 day, found in a sample of 76 cool supergiants observed by \\tess at two-minute cadence. These pulsating YSGs are concentrated in a HR diagram region not previously associated with pulsations; we conclude that this is a genuine new class of pulsating star, Fast Yellow Pulsating Supergiants (FYPS). For each FYPS, we extract frequencies via iterative prewhitening and conduct a time-frequency analysis. One FYPS has an extracted frequency that is split into a triplet, and the amplitude of that peak is modulated on the same timescale as the frequency spacing of the triplet; neither rotation nor binary effects are likely culprits. We discuss the evolutionary status of FYPS and conclude that they are candidate post-RSGs. All stars in our sample also show the same stochastic low-frequency variability (SLFV) found in hot OB stars and attributed to internal gravity waves. Finally, we find four $\\alpha$ Cygni variables in our sample, of which three are newly discovered.",
  "revisions": [
    {
      "version": "v1",
      "updated": "2020-08-26T18:00:00.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "short term variability",
      "evolved massive stars",
      "pulsating supergiants",
      "hr diagram",
      "experiencing significant rsg mass loss"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 29,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}